Abstract

An international survey revealed that eleven compounds representing five pesticide types are currently being used on commercial salmon farms for sea lice control. These include two organophosphates (dichlorvos and azamethiphos); three pyrethrin/pyrethroid compounds (pyrethrum, cypermethrin, deltamethrin); one oxidizing agent (hydrogen peroxide); three avermectins (ivermectin, emamectin and doramectin) and two benzoylphenyl ureas (teflubenzuron and diflubenzuron). The number of compounds available in any one country is highly variable, ranging from 9 (Norway) to 6 (Chile, United Kingdom) to 4 (Ireland, Faeroes, Canada) to 2 (US)). Dichlorvos, Azamethiphos and cypermethrin were the most widely used compounds (5 countries) followed by, hydrogen peroxide, ivermectin and emamectin (4 countries each), teflubenzuron (3 countries), diflubenzuron (2 countries), and deltamethrin, pyrethrum and doramectin (1 country each). Although, like trichlorfon, dichlorvos use is being discontinued in several countries notably Norway and the Faeroes. In most instances the availability of sea lice chemotherapeutants is limited, many being used under extra-label veterinary prescription or exemption, and special investigation permits. Access to a broad range of compounds with different modes of action, as well as application methods, has only recently been acquired making assessment of chemotherapy, and therefore integrated pest management, difficult.